Showing papers by "Tulane University published in 1984"

Exact differential equation for the density and ionization energy of a many-particle system

Abstract: The present investigation is concerned with relations studied by Hohenberg and Kohn (1964) and Kohn and Sham (1965). The properties of a ground-state many-electron system are determined by the electron density. The correct differential equation for the density, as dictated by density-functional theory, is presented. It is found that the ground-state density n of a many-electron system obeys a Schroedinger-like differential equation which may be solved by standard Kohn-Sham programs. Results are connected to the traditional exact Kohn-Sham theory. It is pointed out that the results of the current investigations are readily extended to spin-density functional theory.

A semiclasical justification for the use of non-spreading wavepackets in dynamics calculations

Abstract: A justification is given for the use of non-spreading or frozen gaussian packets in dynamics calculations In this work an initial wavefunction or quantum density operator is expanded in a complete set of grussian wavepackets It is demonstrated that the time evolution of this wavepacket expansion for the quantum wavefunction or density is correctly given within the approximations employed by the classical propagation of the avarage position and momentum of each gaussian packet, holding the shape of these individual gaussians fixed The semiclassical approximation is employed for the quantum propagator and the stationary phase approximation for certain integrals is utilized in this derivation This analysis demonstrates that the divergence of the classical trajectories associated with the individual gaussian packets accounts for the changes in shape of the quantum wavefunction or density, as has been suggested on intuitive grounds by Heller The method should be exact for quadratic potentials and this is verified by explicitly applying it for the harmonic oscillator example

Effect of warfarin anticoagulation on survival in carcinoma of the lung, colon, head and neck, and prostate. Final report of VA Cooperative Study #75.

Abstract: VA Cooperative Study #75 was established to test in a controlled, randomized trial the hypothesis that warfarin anticoagulation would favorably affect the course of certain types of malignancy. No differences in survival were observed between warfarin-treated and control groups for advanced non-small cell lung, colorectal, head and neck and prostate cancers. However, warfarin therapy was associated with a significant prolongation in the time to first evidence of disease progression (P = 0.016) and a significant improvement in survival (P = 0.018) for patients with small cell carcinoma of the lung, including the subgroup of patients with disseminated disease at the time of randomization (P = 0.013). A trend toward improved survival with warfarin treatment was observed for the few patients admitted to this study with non-small cell lung cancer who had minimal disease at randomization. These results suggest that warfarin, as a single anticoagulant agent, may favorably modify the course of some, but not all, types of human malignancy, among which is small cell carcinoma of the lung. Further trials of warfarin may be indicated in patients with limited disease who have cell types that failed to respond when advanced disease was present.

Direct connections of rat visual cortex with sensory, motor, and association cortices

Abstract: Each division of rat visual cortex, areas 17, 18a, and 18b, has connections with sensory, motor, and association cortices. These corticocortical connections were sampled using anterograde autoradiographic and retrograde horseradish peroxidase labeling techniques. Area 17 is connected via reciprocal pathways with each division of visual cortex, the posterior one-third of motor area 8, association area 7, and posteroventral area 36 of temporal cortex. It also receives projections from perirhinal areas 13 and 35. Area 18a has reciprocal connections with areas 17 and 18b, a patch in posterior somatosensory area 3, and dorsal auditory area 41. Like area 17, area 18a receives afferents from and projects to the posterior one-third of motor area 8. The connections of area 18a with association cortices are extensive; these regions include parietal areas 7, 39, 40, and 14, posteroventral and dorsal area 36, and perirhinal cortex. Area 18b is connected with areas 17 and 18a, a patch in medial area 3, and dorsal area 41. There are reciprocal projections between area 18b and posterior area 8. As for association cortex, area 18b projects to frontal area 11, area 7, posteroventral and dorsal area 36, and perirhinal cortex. In addition, area 18b receives input from and projects efferents to the dorsal claustrum. Most of the interconnections among areas 17, 18a, and 18b originate from neurons in layers II, III, and V and end in terminal fields in layers I–III and V. In contrast, projections of other sensory, motor, and association cortices to visual cortex originate mainly from neurons in layer V and to a lesser extent from layer II. The reciprocal pathways from visual cortex terminate predominantly in the supragranular layers. In conclusion, these corticocortical pathways provide the basis for cortical visuosensory and visuomotor integration that may aid the rat in the coordination of visually guided behaviors.

Risk of Infection after Penetrating Abdominal Trauma

Abstract: To identify the risk factors for the development of postoperative septic complications in patients with intestinal perforation after abdominal trauma, and to compare the efficacies of single-drug and dual-drug prophylactic antibiotic therapy, we studied 145 patients who presented with abdominal trauma and intestinal perforation at two hospitals between July 1979 and June 1982. Logistic-regression analysis showed that a higher risk of infection (P less than 0.05) was associated with increased age, injury to the left colon necessitating colostomy, a larger number of units of blood or blood products administered at surgery, and a larger number of injured organs. The presence of shock on arrival, which was found to increase the risk of infection when this factor was analyzed individually, did not add predictive power. Patients with postoperative sepsis were hospitalized significantly longer than were patients without infection (13.8 vs. 7.7 days, P less than 0.0001). Both treatment regimens--cefoxitin given alone and clindamycin and gentamicin given together--resulted in similar infection rates, drug toxicity, duration of hospitalization, and costs.

Large-time regularity of viscous surface waves

Abstract: Etude du mouvement d'un fluide visqueux incompressible contenu dans un ocean tridimensionnel de dimensions finies, limite en bas par un sol solide et en haut par une atmosphere a pression constante. La surface superieure se modifie en fonction du mouvement du fluide

Models of Coevolution and Speciation in Plants and Their Pollinators

Abstract: Coevolution of quantitative characters is modeled for populations of plants and specialized pollinators. Reciprocal selective forces on characters in mutualistic species create lines of equilibria for their mean phenotypes. Diversification between geographically isolated pairs of mutualistic populations can thus occur by random genetic drift. In each species the rate of differentiation between populations depends in part on the effective size of local populations of its mutualistic partner. Sexual selection in a pollinator species, through mating preferences in one sex based on the pollination behavior of the opposite sex, can produce rapid coevolution and speciation in both the pollinator and the plant populations. Patterns of mutualistic coevolution are discussed with particular reference to population structure, ecological interactions, and species diversity in orchids and orchid bees, figs and fig wasps, and yuccas and yucca moths.

Acute combined posterior cruciate and posterolateral instability of the knee

Abstract: This report concerns 13 consecutive patients (13 knees) who underwent operative treatment for acute combined posterior cruciate and posterolateral instabil ity due to combined injury to the posterior cruciate ligament and the arcuate ligament complex. Our pur pose was to examine the method of diagnosis and the results in these patients. There were 12 males and 1 female (average age, 26 years). Five patients were injured in a motor vehicle accident, four in sports activ ities, and four in nonsports activities. The mechanism of injury was an anteromedial blow to the flexed knee in six patients, a fall onto the knee in two, and unknown in five patients. Eleven patients were available for fol low-up evaluation (average, 56 months), and in each the result was rated as good, fair, or poor. In 10 patients (90%) the results were rated as good subjectively, in 11 (100%) as good functionally, and in 8 (73%) as good objectively. Injury to both the posterior cruciate liga ment and the arcuate ligament complex can res...

Immunocytochemical localization of growth hormone-releasing factor in the rat hypothalamus.

Abstract: The distribution of GRF-immunoreactive structures in the rat hypothalamus was studied after colchicine treatment with peroxidase-antiperoxidase immunocytochemistry in vibratome sections. The majority of the GRF-immunoreactive cell bodies were found in the arcuate nucleus and the medial perifornical region of the lateral hypothalamus. Scattered cells were seen in the lateral basal hypothalamus, the medial and lateral portions of the ventromedial nucleus, and the dorsome-dial and paraventricular nuclei. Fibers from the perifornical cell bodies formed a fan-like projection to the median eminence, where a dense accumulation of GRF-containing processes and terminals was found. GRF terminals were located in the central regions of the median eminence. The localization of GRF-im-munoreactive structures in the hypothalamus and median eminence reinforces the view that GRF plays a physiological role in the regulation of pituitary function. (Endocrinology 114: 1082, 1984)

Dimethyl triazeno imidazole carboxamide and combination therapy for melanoma. IV. Late results after complete response to chemotherapy (Central Oncology Group protocols 7130, 7131, and 7131A).

Abstract: The results of three Phase III studies of DTIC in 580 patients with metastatic melanoma were reviewed to evaluate the subsequent course of 26 patients who achieved a complete response (CR) to chemotherapy. The majority (17 of 26) of these patients had soft tissue metastases. Six of the 26 patients remained in CR at last report (30-259 weeks), two died of other causes while remaining free of melanoma, and 18 relapsed and died. Ninety-five percent of the 26 patients were alive at 1 year, and survival was 31.1% at 72 months. Seven of the eight patients with sustained remission received chemotherapy for at least 6 months after CR developed, whereas 10 of 18 relapsing patients were treated for less than 6 months after CR was achieved. Long-term sustained CR to chemotherapy occurs in 1% to 2% of patients treated with DTIC, and late relapse is rare in patients who remain in CR for 2 years.

Can Arms Races Lead to the Outbreak of War

Abstract: The relationships between an arms race and the outbreak of war have been debated over many years. Indeed, the question of war outbreak is the most basic and fundamental one in any study of arms races. This question obviously carries much more urgency when it becomes that of whether a nuclear arms race might lead to a nuclear war. That is the focus of the present paper: the relationships between a nuclear arms race and the outbreak of nuclear war in a bipolar world of two nuclear powers. The paper also presents a specific application to the United States-Soviet Union arms race of the post-war period.

Excitation of hippocampal pyramidal cells by an electrical field effect

Abstract: The effects of electrical fields from antidromic stimulation of CA1 pyramidal cells were studied in slices of rat hippocampus in which chemical synaptic transmission had been blocked by superfusion with physiological solution containing Mn2+ and lowered concentration of Ca2+. Differential voltage recordings were made between two microelectrode positions, on intracellular to a pyramidal cell and the other in the adjacent extracellular space. This technique revealed brief transmembrane depolarizations that occurred synchronously with negative-going extracellular population spikes in the adjacent cell body layer. Glial cells in this region did not exhibit these depolarizations. In some pyramidal cells, alvear stimulation that was too weak to excite the axon of the impaled cell elicited action potentials, which appeared to arise from transmembrane depolarizations at the soma. When subthreshold transmembrane depolarizations were superimposed on subthreshold depolarizing current pulses, somatic action potentials were generated synchronously with the antidromic population spikes. The depolarizations of pyramidal somata were finely graded with stimulus intensity, were unaffected by polarization of the membrane, and were not occluded by preceding action potentials. The laminar profile of extracellular field potentials perpendicular to the cell body layer was obtained with an array of extracellular recording locations. Numerical techniques of current source-density analysis indicated that at the peak of the somatic population spike, there was an extracellular current sink near pyramidal somata and sources in distal dendritic regions. It is concluded that during population spikes an extracellular electrical field causes currents to flow passively across inactive pyramidal cell membranes, thus depolarizing their somata. The transmembrane depolarizations associated with population spikes would tend to excite and synchronize the population of pyramidal cells.

Analysis of intracellularly recorded phasic bursting by mammalian neuroendocrine cells

Abstract: Phasic bursting by magnocellular neuroendocrine cells (MNCs) in the mammalian supraoptic and paraventricular nuclei (SON and PVN) consists of successive periods of action potentials and inactivity. It has previously been correlated with increased release of vasopressin from the neurohypophysis. In the present studies we investigated the neuronal mechanisms underlying this firing pattern. Using coronal slices of rat hypothalamus, we recorded intracellularly from neurons that are considered to be MNCs, based on several criteria. Eight of the 29 cells in this study displayed phasic burst patterns similar to those previously recorded extracellularly from MNCs in intact animals. Among the eight phasic cells, low levels of steady current injection could dramatically alter burst periodicity. Steady hyperpolarization revealed patterned synaptic input in only one case; in the remainder of the cells, nonsynaptic mechanisms appeared to account for periodic bursting. The phasic burst pattern usually appeared to be spike dependent, each burst arising from one or several depolarizing after-potentials (DAPs). Summed DAPs formed a plateau potential, which provided a depolarizing drive for further spiking. Spike frequency decreased late in the burst, and then the plateau potential terminated. During the quiescent period, burst excitability appeared to increase coincident with a small slow depolarization. Spikes and their summating DAPs could then initiate another burst. In several silent MNCs, a brief supra-threshold current pulse could initiate a prolonged afterdischarge, which had the properties of a phasic burst. Two MNCs that fired with a fast-continuous pattern were tested with brief hyperpolarizing current pulses; after each pulse, spike activity ceased and a plateau potential was revealed. Therefore, it appears that a maintained plateau potential (summed DAPs) can drive fast-continuous firing. In one case a periodic bombardment of excitatory postsynaptic potentials (EPSPs) generated a phasic firing pattern. The dependence of the burst characteristics on membrane potential, the apparent lack of patterned synaptic input in most cells, and the ability to evoke bursts with brief stimuli support the hypothesis that bursting in some MNCs involves an endogenous mechanism. Furthermore, phasic firing may be driven by tonic excitatory input. The data on phasic, silent, and fast-continuous cells suggest that many MNCs can generate DAPs and plateau potentials.

Arthroscopy of the shoulder: Technique and normal anatomy:

Abstract: We present our technique of diagnostic and surgical arthroscopy of the shoulder and describe the normal and normal variational arthroscopic anatomy of the structures within the shoulder joint. To ensure accuracy, strict attention is given to consistent patient position and technical detail. Posterior and anterior portals are consistently located with the aid of bony anatomic landmarks. Using a large diameter angled arthroscope, structures within the shoulder joint are identified and examined in sequential order. Diagnostic arthroscopy of the shoulder can be systematic and reproducible when the surgeon is knowledgeable of the normal and normal variational anatomy of the shoulder and when attention is given to accurate placement of the arthroscopic portals and to consistent surgical technique.

Antitumor effects of analogs of hypothalamic hormones in endocrine-dependent cancers.

Abstract: A new approach to the treatment of endocrine-dependent tumors based on analogs of hypothalamic hormones is in the early stages of development, but appears promising and significant. Administration of hypothalamic hormones can mimic hypophysectomy and gonadectomy, and is essentially devoid of side effects. A successful use of agonistic analogs of LH-RH for treatment of endocrine-dependent prostate cancer has been documented in several hundred patients. Experimental studies suggest that agonists and/or antagonists of LH-RH might be useful for treatment of breast cancer and pituitary tumors. Our work in animal models also indicates that analogs of somatostatin, alone or combined with LH-RH agonists, could be considered for therapy of chondrosarcomas, osteosarcomas, and pancreatic cancer. Experiments are in progress on the use of LH-RH analogs for treatment of ovarian cancer, neoplasms of the female genital tract, and for protection against gonadal damage during chemotherapy. These investigations should extend the concepts of endocrine treatment of cancers.

Synchronization without active chemical synapses during hippocampal afterdischarges.

Abstract: Afterdischarges elicited by antidromic stimulation were studied in the CA1 region of transverse slices of rat hippocampus. The slices were incubated in a static bathing medium containing Mn2+ with lowered Ca2+ concentration, which blocked chemical synaptic transmission. Extracellular voltage recordings from micropipettes revealed afterdischarges of population spikes, which represent synchronized action potentials. Afterdischarge duration became longer with incubation time, occasionally lasting up to 9 s. Simultaneous recordings from three extracellular micropipettes indicated propagation of individual population spikes along the CA1 cell body layer during an afterdischarge. Intracellular recordings from pyramidal cells showed that action potentials were synchronized with population spikes. When initial action potentials of an afterdischarge were blocked by hyperpolarizing the impaled cell, subsequent action potentials remained synchronized with population spikes, indicating a synchronizing interaction between neurons. Intrasomatic neuronal recordings sometimes revealed partial action potentials that were also synchronized with population spikes. During afterdischarges, relatively weak (10 mV) hyperpolarization blocked both full and partial action potentials. These observations suggest that synchronized action potentials and partial spikes were initiated near the soma. Intracellular voltage recordings were referenced to a local extracellular microelectrode in order to determine more accurately the transmembrane potential in the presence of large population spikes .54). Such neuronal recordings revealed brief transmembrane depolarizations that occurred synchronously with population spikes. Large injected hyperpolarizing currents did not affect the brief transmembrane depolarizations. Similar differential voltage recordings across glial cell membranes did not show measurable brief transmembrane depolarizations during population spikes. However, slow glial depolarizations during afterdischarges indicated prolonged K+ accumulation and clearance in the extracellular space, which probably contributed to the hyperexcitability of pyramidal cells. During an afterdischarge, extracellular potentials were recorded simultaneously from six micropipettes arranged perpendicularly to the stratum pyramidale. Current source-density analysis indicated a sink in the cell body layer during population spikes and a corresponding source in distal dendrites. It is concluded that an electrical field effect depolarizes and thus synchronizes neurons during these afterdischarges.(ABSTRACT TRUNCATED AT 400 WORDS)

Gift of the devil: A history of Guatemala

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Intrinsic inhibition in magnocellular neuroendocrine cells of rat hypothalamus.

Abstract: Endogenous mechanisms of inhibition in magnocellular neuroendocrine cells were studied with intracellular recordings in the rat hypothalamic slice preparation. Hyperpolarizing after-potentials (duration up to 125 ms) followed single action potentials and after-hyperpolarizations (a.h.p.s) lasting hundreds of milliseconds followed brief evoked spike trains. The amplitude and duration of the a.h.p. increased after spike trains of longer duration or higher frequency. The a.h.p. appears endogenous, rather than synaptically mediated from recurrent inhibition, because it persisted after pharmacological blockade of axonal conduction or of chemical synaptic transmission. The reversal potential of the a.h.p. was at least 20 mV more negative than that of inhibitory post-synaptic potentials. Cl- ionophoresis did not alter the a.h.p. Chelation of intracellular Ca2+ with EGTA injection eliminated the a.h.p. A Ca2+-activated K+ conductance, rather than recurrent synaptic inhibition, apparently causes the a.h.p. and is at least partly responsible for the inhibition after single spikes in magnocellular neurones. During hormone release, this endogenous mechanism may contribute to the post-burst silent period in putative oxytocinergic cells and to the interburst interval in phasic neurones, which are known to fire repetitive bursts associated with vasopressin release.

Proprioception of the knee joint. Paradoxical effect of training.

Abstract: Two tests frequently used to measure joint proprioception were performed on the knees of twelve members of a professional ballet company to determine the effect of extensive athletic training on this sensation. These tests measured the threshold of perception of joint motion and the ability of a subject to reproduce a joint position. A healthy, active age-matched control group was also tested. Results show that dancers performed significantly better on the threshold test (p less than 0.05) and significantly worse when reproducing a joint position (p less than 0.05) than the control group. The strong implication is that athletic training can affect joint proprioception and that these two tests are in fact, dependent on different neural mechanisms.

Isolation of a feline leukaemia provirus containing the oncogene myc from a feline lymphosarcoma

Abstract: The molecular mechanism by which feline leukaemia virus (FeLV) induces lymphoid malignancy in domestic cats is largely unknown. Using the insertional activation model of c-myc by avian leukosis virus in the induction of bursal lymphoma in chickens, we have now characterized the c-myc locus in feline tissues and investigated the possibility that FeLV may also insert within feline c-myc. We used the 1.5 kilobase (kb) PstI fragment of MC29 v-myc in Southern blot analysis to characterize the structure of the c-myc locus in the DNA of 31 naturally occurring feline lymphomas. Analysis of a cloned c-myc gene from one lymphoma demonstrated that sequences homologous to v-myc occupy 2.6 kb of feline DNA in which a putative intron of 0.5 kb separates sequences homologous to the 5' and 3' exons represented in avian v-myc. We also observed in the DNA of this lymphoma tumour-specific fragments homologous to v-myc. Characterization of these molecularly cloned myc-hybridizing fragments revealed the presence of at least two identical FeLV proviruses 5.5 kb in length, each containing long terminal repeats enclosing a spliced version of the feline myc gene.

Studies on the anti-inflammatory properties of thalidomide: Effects on polymorphonuclear leukocytes and monocytes

Abstract: The effects of thalidomide on polymorphonuclear leukocyte (PMN) and monocyte function were studied in vitro. Phagocytosis of latex beads by both PMNs and adherent monocytes was significantly depressed (p µ g/ml of thalidomide. Concentrations of 1 µ g/ml stimulated monocyte Phagocytosis (p µ g/ml resulted in a significant reduction of chemiluminescence (CL) but had no effect at 1 µ /ml concentrations. There was no significant action on PMN CL at either concentration. Finally, 10 , µ g/ml concentrations of thalidomide were not cytotoxic for either cell type after 18-hour incubations. In conclusion, the results of these studies may at least partially explain the efficacy of thalidomide in some inflammatory conditions.

Mechanical modeling of the stress adaptation process in bone

Abstract: The philosophy, techniques, and concepts involved in the mechanical modeling of the process of stress adaptation in bone are described here. First, the idea of a control surface, across which all mechanical forces and fluid transport are monitored, is introduced and employed to totally enclose a living whole bone. Then the mechanical forces are related to local tissue stresses and the fluid transport to the local microcirculation. The concepts of strain, stress, and elasticity are introduced next and the applications of these concepts to biological tissue are discussed. It is argued that biological tissue can only sense strain and not stress; thus baroreceptors are, in fact, strain receptors. The concept of remodeling or stress adaptive equilibrium is then introduced and associated with a particular range of strain values called the band of remodeling equilibrium strains. The deposition or resorption of bone tissue is hypothesized to be a function of the amount of strain by which the actual strain at an anatomical site differs from values of strain in the band of remodeling equilibrium strains. The form of this functional dependence is discussed with regard to a number of points, including its variance from anatomical site to site and the particular features of the strain history which are the most significant in enhancing bone remodeling. In the closing section of the paper, the basic mechanistic ideas underlying our models of bone stress adaptation are presented. These are mechanical models for internal bone remodeling (remodeling) and surface bone remodeling (modeling).